Commercial services which employ a W-CDMA (Wideband Code division Multiple Access) method which is included in communication methods called a third generation were started in Japan since 2001. Furthermore, a service with HSDPA (High Speed Down Link Packet Access) which implements a further improvement in the speed of data transmission using downlinks (a dedicated data channel and a dedicated control channel) by adding a channel for packet transmission (HS-DSCH: High Speed-Downlink Shared Channel) to the downlinks has been started. In addition, an HSUPA (High Speed Up Link Packet Access) method has also been standardized in order to further speed up uplink data transmission. The W-CDMA is a communication method which was determined by the 3GPP (3rd Generation Partnership Project) which is the organization of standardization of mobile communication systems, and the technical specification of the release 7 has been being organized currently.
In the 3GPP, as a communication method different from the W-CDMA, a new communication method having a wireless section, which is referred to as “Long Term Evolution” (LTE), and a whole system configuration including a core network, which is referred to as “System Architecture Evolution” (SAE), has also been studied. The LTE has an access method, a radio channel structure, and protocols which are completely different from those of the current W-CDMA (HSDPA/HSUPA). For example, while the W-CDMA uses, as its access method, code division multiple access (Code Division Multiple Access), the LTE uses, as its access method, OFDM (Orthogonal Frequency Division Multiplexing) for the downlink direction and uses SC-FDMA (Single Career Frequency Division Multiple Access) for the uplink direction. Furthermore, while the W-CDMA has a bandwidth of 5 MHz, the LTE enables each base station to select one bandwidth from among bandwidths of 1.4/3/5/10/15/20 MHz. In addition, the LTE does not include a circuit switching method, unlike the W-CDMA, but uses only a packet communication method.
According to the LTE, because a communication system is configured using a new core network different from a core network (GPRS) in the W-CDMA, the communication system is defined as an independent radio access network which is separate from a W-CDMA network. Therefore, in order to distinguish from a communication system which complies with the W-CDMA, in a communication system which complies with the LTE, a base station (Base station) which communicates with a mobile terminal (UE: User Equipment) is referred to as eNB (E-UTRAN NodeB), and a base station control apparatus (Radio Network Controller) which performs exchange of control data and user data with a plurality of base stations is referred to as an EPC (Evolved Packet Core) (may be called aGW: Access Gateway). This communication system which complies with the LTE provides a y unicast (Unicast) service and an E-MBMS service (Evolved Multimedia Broadcast Multicast Service). An E-MBMS service is a broadcast type multimedia service, and simply may be referred to as an MBMS. A large-volume broadcast content, such as news, a weather forecast, or a mobile broadcasting content, is transmitted to a plurality of mobile terminals. This service is also referred to as a point-to-multipoint (Point to Multipoint) service.
Matters currently determined in the 3GPP and regarding a whole architecture (Architecture) in an LTE system are described in nonpatent reference 1. The whole architecture (chapter 4 of nonpatent reference 1) will be explained with reference to FIG. 1. FIG. 1 is an explanatory drawing showing the configuration of a communication system using an LTE method. In FIG. 1, if a control protocol (e.g., RRC (Radio Resource Management)) and a user plane (e.g., PDCP: Packet Data Convergence Protocol, RLC: Radio Link Control, MAC: Medium Access Control, PHY: Physical layer) for a mobile terminal 101 are terminated at a base station 102, E-UTRAN (Evolved Universal Terrestrial Radio Access) is constructed of one or more base stations 102. Each base station 102 carries out scheduling (Scheduling) and transmission of a paging signal (Paging Signaling, which is also referred to as paging messages (paging messages)) which is transmitted thereto from an MME 103 (Mobility Management Entity). The base stations 102 are connected to one another via X2 interfaces. Furthermore, each base station 102 is connected to an EPC (Evolved Packet Core) via an S1 interface. More specifically, each base station is connected to an MME 103 (Mobility Management Entity) via an S1_MME interface, and is also connected to an S-GW 104 (Serving Gateway) via an S1_U interface. Each MME 103 distributes a paging signal to one or more base stations 102. Furthermore, each MME 103 carries out mobility control (Mobility control) of an idle state (Idle State). Each S-GW 104 carries out transmission and reception of user data to and from one or more base stations 102.
Matters currently determined in the 3GPP and regarding a frame structure in a LTE system are described in nonpatent reference 1 (Chapter 5). The currently determined matters will be explained with reference to FIG. 2. FIG. 2 is an explanatory drawing showing the configuration of a radio frame for use in a communication system using an LTE method. In FIG. 2, one radio frame (Radio frame) has a time length of 10 ms. Each radio frame is divided into ten equal-sized subframes (Subframes). Each subframe is divided into two equal-sized slots (slots). A downlink synchronization channel (Downlink Synchronization Channel: SCH) is included in each of the 1st (#0) and 6th subframes (#5) of each frame. Synchronization signals include a primary synchronization channel (Primary Synchronization Channel: P-SCH) and a secondary synchronization channel (Secondary Synchronization Channel: S-SCH). Multiplexing of a channel used for MBSFN (Multimedia Broadcast multicast service Single Frequency Network) and a channel used for other than MBSFN is carried out for each subframe. Hereafter, a subframe used for MBSFN transmission is referred to as an MBSFN subframe (MBSFN subframe). In nonpatent reference 2, an example of signaling at the time of allocation of MBSFN subframes is described. FIG. 3 is an explanatory drawing showing the configuration of an MBSFN frame. In FIG. 3, MBSFN subframes are allocated to each MBSFN frame (MBSFN frame). An MBSFN frame cluster (MBSFN frame Cluster) is scheduled. The repetition period (Repetition Period) of an MBSFN frame cluster is allocated.
Matters currently determined in the 3GPP and regarding a channel structure in an LTE system are described in nonpatent reference 1. Physical channels (Physical channels) (chapter 5 of nonpatent reference 1) will be explained with reference to FIG. 4. FIG. 4 is an explanatory drawing explaining physical channels for use in a communication system using an LTE method. In FIG. 4, a physical broadcast channel 401 (Physical Broadcast channel: PBCH) is a downlink channel which is transmitted from a base station 102 to a mobile terminal 101. A BCH transport block (transport block) is mapped onto four subframes during a 40-ms time period. There is no clear signaling having a timing of 40 ms. A physical control channel format indicator channel 402 (Physical Control format indicator channel: PCFICH) is transmitted from the base station 102 to the mobile terminal 101. The PCFICH informs the number of OFDM symbols used for PDCCHs from the base station 102 to the mobile terminal 101. The PCFICH is transmitted in each subframe. A physical downlink control channel 403 (Physical downlink control channel: PDCCH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. The PDCCH informs resource allocation (allocation), HARQ information about a DL-SCH (a downlink shared channel which is one of transport channels shown in FIG. 5), and a PCH (paging channel which is one of the transport channels shown in FIG. 5). The PDCCH carries an uplink scheduling grant (Uplink Scheduling Grant). The PDCCH also carries ACK/Nack which is a response signal showing a response to uplink transmission. A physical downlink shared channel 404 (Physical downlink shared channel: PDSCH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. A DL-SCH (downlink shared channel) which is a transport channel is mapped onto the PDSCH. A physical multicast channel 405 (Physical multicast channel: PMCH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. An MCH (multicast channel) which is a transport channel is mapped onto the PMCH.
A physical uplink control channel 406 (Physical Uplink control channel: PUCCH) is an uplink channel transmitted from the mobile terminal 101 to the base station 102. The PUCCH carries ACK/Nack which is a response signal (response) which is a response to downlink transmission. The PUCCH carries a CQI (Channel Quality indicator) report. The CQI is quality information showing either the quality of received data or communication channel quality. A physical uplink shared channel 407 (Physical Uplink shared channel: PUSCH) is an uplink channel transmitted from the mobile terminal 101 to the base station 102. A UL-SCH (an uplink shared channel which is one of the transport channels shown in FIG. 5) is mapped onto the PUSCH. A physical HARQ indicator channel 408 (Physical Hybrid ARQ indicator channel: PHICH) is a downlink channel transmitted from the base station 102 to the mobile terminal 101. The PHICH carries ACK/Nack which is a response to uplink transmission. A physical random access channel 409 (Physical random access channel: PRACH) is an uplink channel transmitted from the mobile terminal 101 to the base station 102. The PRACH carries a random access preamble (random access preamble).
The transport channels (Transport channels) (chapter 5 of nonpatent reference 1) will be explained with reference to FIG. 5. FIG. 5 is an explanatory drawing explaining the transport channels for use in a communication system using an LTE method. Mapping between downlink transport channels and downlink physical channels is shown in FIG. 5A. Mapping between uplink transport channels and uplink physical channels is shown in FIG. 5B. In the downlink transport channels, a broadcast channel (Broadcast channel: BCH) is broadcast to all the base stations (cell). The BCH is mapped onto a physical broadcast channel (PBCH). Retransmission control with HARQ (Hybrid ARQ) is applied to a downlink shared channel (Downlink Shared channel: DL-SCH). Broadcasting to all the base stations (cell) can be carried out. Dynamic or semi-static (Semi-static) resource allocation is supported. Semi-static resource allocation is also referred to as persistent scheduling (Persistent Scheduling). DRX (Discontinuous reception) by a mobile terminal is supported in order to achieve low power consumption of the mobile terminal. The DL-SCH is mapped onto a physical downlink shared channel (PDSCH). A paging channel (Paging channel: PCH) supports DRX by a mobile terminal in order to enable the mobile terminal to achieve low power consumption. Broadcasting to all the base stations (cell) is requested. Mapping onto either a physical resource such as a physical downlink shared channel (PDSCH) which can be dynamically used for traffic, or a physical resource such as a physical downlink control channel (PDCCH) which is another control channel is carried out. A multicast channel (Multicast channel: MCH) is used for the broadcasting to all the base stations (cell). SFN combining of MBMS services (MTCH and MCCH) in multi-cell transmission is supported. Semi-static resource allocation is supported. The MCH is mapped onto a PMCH.
Retransmission control with HARQ (Hybrid ARQ) is applied to an uplink shared channel (Uplink Shared channel: UL-SCH). Dynamic or semi-static (Semi-static) resource allocation is supported. A UL-SCH is mapped onto a physical uplink shared channel (PUSCH). A random access channel (Random access channel: RACH) shown in FIG. 5B is limited to control information. There is a risk of collision. The RACH is mapped onto a physical random access channel (PRACH). HARQ will be explained hereafter.
HARQ is a technology of improving the communication quality of a transmission line by using a combination of automatic retransmission (Automatic Repeat reQuest) and error correction (Forward Error Correction). Retransmission provides an advantage of making an error correction function be effective also for a transmission line whose communication quality varies. Particularly, when performing retransmission, combining the results of reception of first-time transmission and the results of reception of retransmission provides a further improvement in the quality. An example of a retransmission method will be explained. When a receive side cannot decode received data correctly (when a CRC Cyclic Redundancy Check error occurs (CRC=NG)), the receive side transmits “Nack” to the transmit side. When receiving “Nack”, the transmit side retransmits the data. In contrast, when the receive side can decode the received data correctly (when no CRC error occurs (CRC=OK)), the receive side transmits “Ack” to the transmit side. When receiving “Ack”, the transmit side transmits the next data. There is “chase combining” (Chase Combining) as an example of a HARQ method. The chase combining is a method of transmitting the same data sequence at the time of first-time transmission and at the time of retransmission, and, when performing retransmission, combining the data sequence at the first-time transmission and the data sequence at the retransmission to improve the gain. This is based on an idea that even if the first-time transmission data has an error, the first-time transmission data partially includes correct data, and therefore the data can be transmitted with a higher degree of precision by combining the correct portion of the first-time transmission data and the retransmission data. Furthermore, there is IR (Incremental Redundancy) as another example of the HARQ method. The IR is a method of increasing the degree of redundancy with a combination with the first-time transmission by transmitting a parity bit at the time of retransmission to improve the quality by using an error correction function.
Logical channels (Logical channels) (chapter 6 of nonpatent reference 1) will be explained with reference to FIG. 6. FIG. 6 is an explanatory drawing explaining logical channels for use in a communication system using an LTE method. Mapping between downlink logical channels and downlink transport channels is shown in FIG. 6A. Mapping between uplink logical channels and uplink transport channels is shown in FIG. 6B. A broadcast control channel (Broadcast control channel: BCCH) is a downlink channel for broadcast system control information. The BCCH which is a logical channel is mapped onto either a broadcast channel (BCH) which is a transport channel, or a downlink shared channel (DL-SCH). A paging control channel (Paging control channel: PCCH) is a downlink channel for transmitting a paging signal. The PCCH is used when the network does not know the cell location of a mobile terminal. The PCCH which is a logical channel is mapped onto a paging channel (PCH) which is a transport channel. A common control channel (Common control channel: CCCH) is a channel for transmission control information between a mobile terminal and a base station. The CCCH is used when the mobile terminal does not have RRC connection (connection) between the mobile terminal and the network. Whether to dispose the CCCH for downlink is not decided at this time. In the uplink direction, the CCCH is mapped onto an uplink shared channel (UL-SCH) which is a transport channel.
A multicast control channel (Multicast control channel: MCCH) is a downlink channel for point-to-multipoint transmission. The channel is used for transmission of MBMS control information for one or some MTCHs from the network to mobile terminals. The MCCH is used only for a mobile terminal currently receiving an MBMS. The MCCH is mapped onto either a downlink shared channel (DL-SCH) which is a transport channel, or a multicast channel (MCH). A dedicated control channel (Dedicated control channel: DCCH) is a channel for transmitting dedicated control information between a mobile terminal and the network. The DCCH is mapped onto an uplink shared channel (UL-SCH) in the uplink, and is mapped onto a downlink shared channel (DL-SCH) in the downlink. A dedicated traffic channel (Dedicate Traffic channel: DTCH) is a channel of point-to-point communications to each mobile terminal for transmission of user information. The DTCH exists for both the uplink and the downlink. The DTCH is mapped onto an uplink shared channel (UL-SCH) in the uplink, and is mapped onto a downlink shared channel (DL-SCH) in the downlink. A multicast traffic channel (Multicast Traffic channel: MTCH) is a downlink channel for transmission of traffic data from the network to a mobile terminal. The MTCH is used only for a mobile terminal currently receiving an MBMS. The MTCH is mapped onto either a downlink shared channel (DL-SCH) or a multicast channel (MCH).
Matters currently determined in the 3GPP and regarding an E-MBMS service are described in nonpatent reference 1. The definitions of terms regarding E-MBMS (chapter 15 of nonpatent reference 1) will be explained with reference to FIG. 7. FIG. 7 is an explanatory drawing for explaining a relationship between an MBSFN synchronization area and MBSFN areas. In FIG. 7, the MBSFN synchronization area 701 (Multimedia Broadcast multicast service Single Frequency Network Synchronization Area) is a network area in which all the base stations can perform MBSFN (Multimedia Broadcast Multicast service Single Frequency Network) transmission in synchronization with one another. The MBSFN synchronization area includes one or more MBSFN areas (MBSFN Areas) 702. In one frequency layer (frequency layer), each base station can belong only to one MBSFN synchronization area. Each MBSFN area 702 (MBSFN Area) consists of a group of base stations (cell) included in the MBSFN synchronization area of the network. The base stations (cell) in the MBSFN synchronization area may construct a plurality of MBSFN areas.
The logical architecture (Logical Architecture) of E-MBMS (chapter 15 of nonpatent reference 1) will be explained with reference to FIG. 8. FIG. 8 is an explanatory drawing explaining the logical architecture (Logical Architecture) of E-MBMS. In FIG. 8, a multi-cell/multicast coordination entity 801 (Multi-cell/multicast Coordination Entity: MCE) is a logical entity. The MCE 801 allocates radio resources to all the base stations in an MBSFN area in order to carry out multi-cell MBMS transmission (multi-cell MBMS transmission). The MCE 801 makes a decision about the details of radio configuration (e.g., a modulation method and a code) in addition to the allocation of the radio resources in time and/or in frequency. An E-MBMS gateway 802 (MBMS GW) is a logical entity. The E-MBMS gateway 802 is located between an eBMSC and base stations, and has a main function of transmitting and broadcasting an MBMS service to each of the base stations according to a SYNC protocol. An M3 interface is a control interface (Control Plane Interface) between the MCE 801 and the E-MBMS gateway 802. An M2 interface is a control interface between the MCE 801 and an eNB 102. An M1 interface is a user data interface (User Plane Interface) between the E-MBMS gateway 802 and the eNB 803.
The architecture (Architecture) of E-MBMS (chapter 15 of nonpatent reference 1) will be explained. FIG. 9 is an explanatory drawing explaining the architecture (Architecture) of E-MBMS. As to the architecture of E-MBMS, two examples are considered as shown in FIGS. 9A and 9B. Cells (15 of nonpatent reference 1) of MBMS will be explained. In an LTE system, there is an MBMS dedicated cell (base station) (MBMS dedicated cell) and an MBMS/Unicast-mixed cell (MBMS/Unicast-mixed cell) which can carry out both an MBMS service and a unicast service. An MBMS dedicated cell will be explained. Features in a case in which the MBMS dedicated cell belongs to a frequency layer dedicated to MBMS transmission will be described hereafter. Hereinafter, the MBMS transmission dedicated frequency layer is also referred to as an MBMS dedicated cell frequency layer. An MTCH (multicasting traffic channel) and an MCCH (multicast control channel) which are both downlink logical channels are mapped onto either an MCH (multicast channel) which is a downlink transport channel or a DL-SCH (downlink shared channel) in point-to-multipoint transmission. No uplink exists in the MBMS dedicated cell. Furthermore, transmission and reception of unicast data cannot be carried out within the MBMS dedicated cell. Furthermore, no counting mechanism is set up. Whether to provide a paging signal (Paging messages) in the MBMS transmission dedicated frequency layer has not been decided.
Next, an MBMS/Unicast-mixed cell will be explained. Features in a case in which the MBMS/Unicast-mixed cell does not belong to the MBMS transmission dedicated frequency layer will be described hereafter. A frequency layer other than the MBMS transmission dedicated frequency layer is referred to as a “unicast/mixed frequency layer”. An MTCH and an MCCH which are both downlink logical channels are mapped onto either an MCH which is a downlink logical channel or a DL-SCH in point-to-multipoint transmission. In the MBMS/Unicast-mixed cell, both transmission of unicast data and transmission of MBMS data can be carried out.
MBMS transmission (chapter 15 of nonpatent reference 1) will be explained. The MBMS transmission in an LTE system supports single-cell transmission (Single-cell transmission: SC transmission) and multi-cell transmission (multi-cell transmission: MC transmission). An SFN (Single frequency Network) operation is not supported in the single-cell transmission. Furthermore, an SFN operation is supported in the multi-cell transmission. Transmission of an MBMS is synchronized in an MBSFN (Multimedia Broadcast multicast service Single Frequency Network) area. SFN combining (Combining) of MBMS services (MTCH and MCCH) in the multi-cell transmission is supported. An MTCH and an MCCH are mapped onto an MCH in point-to-multipoint transmission. Scheduling is carried out by an MCE.
The structure (Structure) of a multicast control channel (MCCH) (Chapter 15 of nonpatent reference) will be explained. A broadcast control channel (BCCH) which is a downlink logical channel shows scheduling of one or two primary multicast control channels (Primary MCCH: P-MCCH). A P-MCCH for single-cell transmission is mapped onto a DL-SCH (downlink shared channel). A P-MCCH for multi-cell transmission is mapped onto an MCH (multicast channel). In a case in which a secondary multicast control channel (Secondary MCCH: S-MCCH) is mapped on an MCH, the address of the secondary multicast control channel (S-MCCH) can be shown by using a primary multicast control channel (P-MCCH). Although a broadcast control channel (BCCH) shows a resource of a primary multicast control channel (P-MCCH), it does not show any available service.
Matters currently determined in the 3GPP and regarding paging are described in nonpatent reference 1 (chapter 10). A paging group uses an L1/L2 signaling channel (PDCCH). A precise identifier (UE-ID) of a mobile terminal can be checked on a paging channel (PCH).    [Nonpatent reference 1] 3GPP TS36.300 V8.2.0    [Nonpatent reference 2] 3GPP R1-072963    [Nonpatent reference 3] 3GPP R1-080073    [Nonpatent reference 4] 3GPP R2-080463    [Nonpatent reference 5] 3GPP R2-075570    [Nonpatent reference 6] 3GPP TS36.211 V8.4.0    [Nonpatent reference 7] 3GPP TS36.331 V8.3.0    [Nonpatent reference 8] 3GPP TS36.306 V8.2.0